The long term goal of this research program is to provide a basis for detailed studies of the molecular mechanisms of gene regulation in the development of the nervous system and its effector cells. This research project will enjoy a combined metabolic and structural approach to characterize a set of eucaryotic genes whose RNA and protein products are regulated in the processes of cell differentiation and morphogenesis and to determine the molecular mechanisms by which this regulation occurs. Specifically, this will involve the construction of cDNA clones which are comprised of sequences of genes whose expressions are regulated during mammalian myogenic and neuronal developmental programs. The regulation of the expression of the Alpha-, Beta-, and Gamma-actin genes will be studied during the differentiation of the permanent myogenic cell line L6 from myoblast to myotube. In addition, the regulation of the expression of the neuropeptide genes encoding the enkephalins will be analyzed during the NGF and glucocorticoid hormone induced differentiation of the adrenal medullary pheochromocytoma PC12 cell line into embryonic sympathetic-like neurons. The cloned cDNA sequences of these genes will, in turn, be used to identify and isolate clones containing the chromosomal DNA segments which encode the respective mRNAs. These pure DNA sequences will be used to quatitatively analyze the metabolism of these RNAs during various stages of these developmental programs and will include the determination of transcription rates, mechanisms by which the mRNAs are derived from nuclear RNA precursors, nucleo-cytoplasmic transport, and the rates of cytoplasmic degradation. These measurements will identify the transcriptional and post-transcriptional level of regulation. Structural studies will define the transcriptional units and will include the mapping of the flanking, transcribed, and translated sequences of these developmentally regulated genes. The elucidation of molecular mechanisms of gene regulation in these systems should be highly relevant to understanding many other developmental and cellular systems as well as a variety of disease processes. In addition, since very little is known about the structure and regulation of neuropeptide gene systems this study should provide more understanding of such gene systems and also their abnormal ectopic expression by many tumors.